From: Marc Zyngier <marc.zyngier@arm.com>
To: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Cc: Christoffer Dall <christoffer.dall@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Jason Cooper <jason@lakedaemon.net>,
Eric Auger <eric.auger@redhat.com>
Subject: [RFC PATCH 32/33] irqchip/gic-v4: Add some basic documentation
Date: Tue, 17 Jan 2017 10:20:53 +0000 [thread overview]
Message-ID: <1484648454-21216-33-git-send-email-marc.zyngier@arm.com> (raw)
In-Reply-To: <1484648454-21216-1-git-send-email-marc.zyngier@arm.com>
Do a braindump of the way things are supposed to work.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
drivers/irqchip/irq-gic-v4.c | 59 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)
diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c
index 36ccaac..8b2d9ee 100644
--- a/drivers/irqchip/irq-gic-v4.c
+++ b/drivers/irqchip/irq-gic-v4.c
@@ -22,6 +22,65 @@
#include <linux/irqchip/arm-gic-v4.h>
+/*
+ * WARNING: The blurb below assumes that you understand the
+ * intricacies of GICv3, GICv4, and how a guest's view of a GICv3 gets
+ * translated into GICv4 comands. So it effectively targets at most
+ * two individuals. You know who you are.
+ *
+ * The core GICv4 code is designed to *avoid* exposing too much of the
+ * core GIC code (that would in turn leak into the hypervisor code),
+ * and instead provide a hypervisor agnostic interface to the HW (of
+ * course, the astute reader will quickly realize that hypervisor
+ * agnostic actually means KVM-specific - what were you thinking?).
+ *
+ * In order to achieve a modicum of isolation, we try to hide most of
+ * the GICv4 "stuff" behind normal irqchip operations:
+ *
+ * - Any guest-visible VLPI is backed by a Linux interrupt (and a
+ * physical LPI which gets deconfigured when the guest maps the
+ * VLPI). This allows the same DevID/Event pair to be either mapped
+ * to the LPI (host) or the VLPI (guest).
+ *
+ * - Enabling/disabling a VLPI is done by issuing mask/unmask calls.
+ *
+ * - Guest INT/CLEAR commands are implemented through
+ * irq_set_irqchip_state().
+ *
+ * - The *bizarre* stuff (mapping/unmapping an interrupt to a VLPI, or
+ * issuing an INV after changing a priority) gets shoved into the
+ * irq_set_vcpu_affinity() method. While this is quite horrible
+ * (let's face it, this is the irqchip version of an ioctl), it
+ * confines the crap to a single location. And map/unmap really is
+ * about setting the affinity of a VLPI to a vcpu, so only INV is
+ * majorly out of place. So there.
+ *
+ * But handling VLPIs is only one side of the job of the GICv4
+ * code. The other (darker) side is to take care of the doorbell
+ * interrupts which are delivered when a VLPI targeting a non-running
+ * vcpu is being made pending.
+ *
+ * The choice made here is that each vcpu (VPE in old northern GICv4
+ * dialect) gets a single doorbell, no matter how many interrupts are
+ * targeting it. This has a nice property, which is that the interrupt
+ * becomes a handle for the VPE, and that the hypervisor code can
+ * manipulate it through the normal interrupt API:
+ *
+ * - VMs (or rather the VM abstraction that matters to the GIC)
+ * contain an irq domain where each interrupt maps to a VPE. In
+ * turn, this domain stis on top of the normal LPI allocator, and a
+ * specially crafted irq_chip implementation.
+ *
+ * - mask/unmask do what is expected on the doorbell interrupt.
+ *
+ * - irq_set_affinity is used to move a VPE from one redistributor to
+ * another.
+ *
+ * - irq_set_vcpu_affinity once again gets hijacked for the purpose of
+ * creating a new sub-API, namely scheduling/descheduling a VPE and
+ * performing INVALL operations.
+ */
+
static struct irq_domain *its_vpe_domain;
static struct irq_chip its_vcpu_irq_chip = {
--
2.1.4
next prev parent reply other threads:[~2017-01-17 10:47 UTC|newest]
Thread overview: 121+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-17 10:20 [RFC PATCH 00/33] irqchip: Core support for GICv4 Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 01/33] irqchip/gic-v3: Add redistributor iterator Marc Zyngier
2017-02-13 9:39 ` Thomas Gleixner
2017-02-13 21:12 ` Shanker Donthineni
2017-02-16 12:47 ` Auger Eric
2017-06-19 15:26 ` Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 02/33] irqchip/gic-v3: Add VLPI/DirectLPI discovery Marc Zyngier
2017-02-13 9:39 ` Thomas Gleixner
2017-02-13 21:39 ` Shanker Donthineni
2017-02-16 13:19 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 03/33] irqchip/gic-v3-its: Refactor command encoding Marc Zyngier
2017-02-13 9:54 ` Thomas Gleixner
2017-02-16 13:19 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 04/33] irqchip/gic-v3-its: Move LPI definitions around Marc Zyngier
2017-02-13 9:55 ` Thomas Gleixner
2017-02-16 13:22 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 05/33] irqchip/gic-v3-its: Zero command on allocation Marc Zyngier
2017-02-13 9:55 ` Thomas Gleixner
2017-01-17 10:20 ` [RFC PATCH 06/33] irqchip/gic-v3-its: Add probing for VLPI properties Marc Zyngier
2017-02-13 10:00 ` Thomas Gleixner
2017-02-16 13:46 ` Auger Eric
2017-02-13 21:58 ` Shanker Donthineni
2017-01-17 10:20 ` [RFC PATCH 07/33] irqchip/gic-v3-its: Macro-ize its_send_single_command Marc Zyngier
2017-02-13 10:24 ` Thomas Gleixner
2017-02-16 14:59 ` Auger Eric
2017-02-17 6:15 ` Auger Eric
2017-06-19 15:38 ` Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 08/33] irqchip/gic-v3-its: Implement irq_set_irqchip_state for pending state Marc Zyngier
2017-02-13 10:28 ` Thomas Gleixner
2017-02-16 14:59 ` Auger Eric
2017-02-17 6:15 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 09/33] irqchip/gic-v3-its: Split out property table allocation Marc Zyngier
2017-02-13 10:28 ` Thomas Gleixner
2017-02-17 6:15 ` Auger Eric
2017-06-19 15:42 ` Marc Zyngier
2017-02-17 20:40 ` Prakash B
2017-01-17 10:20 ` [RFC PATCH 10/33] irqchip/gic-v4-its: Allow use of indirect VCPU tables Marc Zyngier
2017-02-13 10:28 ` Thomas Gleixner
2017-02-13 22:14 ` Shanker Donthineni
2017-06-19 14:47 ` Marc Zyngier
2017-02-17 6:15 ` Auger Eric
2017-03-16 21:50 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 11/33] irqchip/gic-v3-its: Split out pending table allocation Marc Zyngier
2017-02-13 10:29 ` Thomas Gleixner
2017-02-13 22:31 ` Shanker Donthineni
2017-03-16 8:57 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 12/33] irqchip/gic-v3-its: Rework LPI freeing Marc Zyngier
2017-02-13 10:30 ` Thomas Gleixner
2017-03-16 8:57 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 13/33] irqchip/gic-v3-its: Generalize device table allocation Marc Zyngier
2017-02-13 10:31 ` Thomas Gleixner
2017-03-16 8:57 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 14/33] irqchip/gic-v3-its: Generalize LPI configuration Marc Zyngier
2017-02-13 10:32 ` Thomas Gleixner
2017-03-16 8:57 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 15/33] irqchip/gic-v4: Add management structure definitions Marc Zyngier
2017-02-13 10:33 ` Thomas Gleixner
2017-03-16 8:58 ` Auger Eric
2017-06-19 15:48 ` Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 16/33] irqchip/gic-v3-its: Add GICv4 ITS command definitions Marc Zyngier
2017-02-13 10:34 ` Thomas Gleixner
2017-03-16 8:58 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 17/33] irqchip/gic-v3-its: Add VLPI configuration hook Marc Zyngier
2017-02-13 10:37 ` Thomas Gleixner
2017-02-13 23:07 ` Shanker Donthineni
2017-06-19 14:52 ` Marc Zyngier
2017-03-16 8:59 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 18/33] irqchip/gic-v3-its: Add VLPI map/unmap operations Marc Zyngier
2017-03-16 8:59 ` Auger Eric
2017-06-19 13:08 ` Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 19/33] irqchip/gic-v3-its: Add VLPI configuration handling Marc Zyngier
2017-02-13 10:38 ` Thomas Gleixner
2017-03-16 8:59 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 20/33] irqchip/gic-v3-its: Add VPE domain infrastructure Marc Zyngier
2017-02-13 10:40 ` Thomas Gleixner
2017-06-19 13:54 ` Marc Zyngier
2017-03-16 9:18 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 21/33] irqchip/gic-v3-its: Add VPE irq domain allocation/teardown Marc Zyngier
2017-02-13 10:45 ` Thomas Gleixner
2017-02-13 23:25 ` Shanker Donthineni
2017-03-16 9:27 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 22/33] irqchip/gic-v3-its: Add VPE irq domain [de]activation Marc Zyngier
2017-02-13 10:45 ` Thomas Gleixner
2017-01-17 10:20 ` [RFC PATCH 23/33] irqchip/gic-v3-its: Add VPENDBASER/VPROPBASER accessors Marc Zyngier
2017-02-13 10:46 ` Thomas Gleixner
2017-02-13 23:39 ` Shanker Donthineni
2017-06-19 15:03 ` Marc Zyngier
2017-03-16 21:03 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 24/33] irqchip/gic-v3-its: Add VPE scheduling Marc Zyngier
2017-02-13 10:48 ` Thomas Gleixner
2017-02-14 0:13 ` Shanker Donthineni
2017-06-19 15:23 ` Marc Zyngier
2017-02-14 1:24 ` Shanker Donthineni
2017-03-16 21:23 ` Auger Eric
2017-03-16 21:41 ` Shanker Donthineni
2017-06-19 9:34 ` Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 25/33] irqchip/gic-v3-its: Add VPE invalidation hook Marc Zyngier
2017-02-13 10:48 ` Thomas Gleixner
2017-01-17 10:20 ` [RFC PATCH 26/33] irqchip/gic-v3-its: Add VPE affinity changes Marc Zyngier
2017-02-13 10:56 ` Thomas Gleixner
2017-01-17 10:20 ` [RFC PATCH 27/33] irqchip/gic-v3-its: Add VPE interrupt masking Marc Zyngier
2017-02-13 10:57 ` Thomas Gleixner
2017-03-16 21:58 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 28/33] irqchip/gic-v3-its: Support VPE doorbell invalidation even when !DirectLPI Marc Zyngier
2017-02-13 11:15 ` Thomas Gleixner
2017-02-14 0:44 ` Shanker Donthineni
2017-06-19 13:31 ` Marc Zyngier
2017-01-17 10:20 ` [RFC PATCH 29/33] irqchip/gic-v4: Add per-VM VPE domain creation Marc Zyngier
2017-02-13 11:16 ` Thomas Gleixner
2017-01-17 10:20 ` [RFC PATCH 30/33] irqchip/gic-v4: Add VPE command interface Marc Zyngier
2017-02-13 11:16 ` Thomas Gleixner
2017-03-16 21:17 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 31/33] irqchip/gic-v4: Add VLPI configuration interface Marc Zyngier
2017-02-13 11:17 ` Thomas Gleixner
2017-03-16 21:08 ` Auger Eric
2017-01-17 10:20 ` Marc Zyngier [this message]
2017-02-13 11:17 ` [RFC PATCH 32/33] irqchip/gic-v4: Add some basic documentation Thomas Gleixner
2017-03-16 21:02 ` Auger Eric
2017-01-17 10:20 ` [RFC PATCH 33/33] irqchip/gic-v4: Enable low-level GICv4 operations Marc Zyngier
2017-02-13 11:17 ` Thomas Gleixner
2017-02-13 11:19 ` [RFC PATCH 00/33] irqchip: Core support for GICv4 Thomas Gleixner
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